Hereinbelow, the problems experienced in a conventional technique relating to the present invention will be described.
Vehicle seats function to maintain sitting postures of vehicle passengers and are typically divided into separate seats, which are designed to allow one person to sit thereon and are installed in the front section of the passenger compartment of a vehicle, thereby forming a driver's seat and a front passenger seat, and bench-type seats or multi-row seats that are designed to allow several persons to sit thereon and are installed in the rear section of the passenger compartment.
The vehicle seat includes: a metal frame that forms a frame of the seat; a seat cushion that covers the frame and comes into contact with the body of a passenger so that, in addition to supporting the body of the passenger and maintaining the posture of the passenger, the seat cushion allows the passenger to feel comfortable; and a seat back.
The vehicle seat is located on a seat rail, which includes a lower rail that is mounted to the floor of a car body and an upper rail that is coupled to the lower rail in such a way that the upper rail can slide along the lower rail to adjust the location of the seat. To adjust the height of the seat cushion, there is provided a seat height adjusting device, in which a link unit is provided in the seat rail and an adjusting handle is provided outside the seat, wherein the link unit is connected to the handle so that the height of the seat cushion can be adjusted.
FIG. 1 is a view schematically illustrating a conventional seat height adjusting device. Hereinbelow, the conventional seat height adjusting device will be described with reference to FIG. 1.
As shown in FIG. 1, the conventional seat height adjusting device 1 includes: a pinion gear 10 that is engaged with a link gear (not shown); a guide unit 20, one end of which is inserted into a shaft hole 100 of the pinion gear 10 and is connected thereto; a sub-spring 30 that is interposed between the outer circumferential surface of a lever connector 200 of the guide unit 20 and the inner circumferential surface of a holding part 201 of the guide unit 20; a brake spring 40 that is fitted over the outer circumferential surface of the holding part 201 of the guide unit 20; and a brake drum 50, in a depressed central portion of which the guide unit 20 having both the sub-spring 30 and the brake spring 40 is seated, and which is provided in the central portion thereof with a shaft hole 500 for receiving the lever connector 200 of the guide unit 20.
In the conventional seat height adjusting device 1 having the above-mentioned construction, there is provided an actuating lever (not shown) that has a dial-type structure. When the actuating lever is actuated in one direction, the lever connector 200 that is connected to the actuating lever is rotated in the same direction so that the guide unit 20 is rotated in the same direction. When the guide unit 20 is rotated in one direction as described above, the pinion gear 10 that is connected to the end of the guide unit 20 is rotated in the same direction and actuates the link gear (not shown) so that the height of the seat cushion can be adjusted.
Here, opposite ends of the brake spring 40 are hooked by opposite sides of the holding part of the guide unit 20, respectively, so that when the guide unit 20 is rotated in the direction as described above, either end of the brake spring 40 is pulled by the holding part of the guide unit 20 and, accordingly, the brake spring 40 is compressed inwards and the outer diameter of the brake spring 40 is reduced. Therefore, no frictional force is generated between the brake spring 40 and the inner circumferential surface of the brake drum 50 so that both the guide unit 20 and the pinion gear 10 can be rotated in the same direction and can adjust the height of the seat cushion.
On the contrary, when an external force is applied to the pinion gear 10, a biasing protrusion 101, which is provided on the pinion gear 10 and is placed between the opposite ends of the brake spring 40, pushes one of the opposite ends of the brake spring 40 in a direction in which the outer diameter of the brake spring 40 increases. Therefore, a frictional force is generated between the brake spring 40 and the inner circumferential surface of the brake drum 50 so that a braking force is generated and fixes the location of the seat cushion, the height of which has been adjusted.
However, the conventional seat height adjusting device 1 produces the braking force using only the frictional force that is generated between the brake spring 40 and the brake drum 50 so that when an excessive external force is applied to the pinion gear 10 and a frictional force is generated between the brake spring 40 and the brake drum 50, the brake spring 40 may move inside the brake drum 50 due to the excessive external force and may not firmly fix the location of the seat cushion, the height of which has been adjusted. This causes an occupant to frequently manipulate the actuating lever so as to repeatedly adjust the height of the seat cushion, thereby causing the occupant inconvenience.
Further, the excessive external force that is applied to the pinion gear 10 may easily deform or break the brake spring 40. The deformed or broken brake spring 40 may fail to maintain a desired and constant clearance between the brake drum 50 and the brake spring 40 so that the conventional seat height adjusting device may not realize the desired operational efficiency. Further, when a user operates the conventional seat height adjusting device using the actuating lever, the operational rotating force is transmitted to the pinion gear 10 through the sub-spring 30 so that the efficiency of transmitting the rotating force is too low and this causes user inconvenience.
Therefore, in an effort to solve the problems that have been experienced in the conventional seat height adjusting device, a pumping device for vehicle seat cushions has been proposed and used in recent years. In a conventional pumping device for vehicle seat cushions, a long actuating lever is repeatedly actuated upwards and downwards in a manner similar to a typical pump handle, thereby adjusting the height of the seat cushion and causing the user convenience when using the pumping device.
However, the conventional pumping device is problematic in that, when the user operates the pumping device so as to adjust the height of the seat cushion, an excessive amount of loss occurs in the operating amounts of both a brake unit and a clutch unit that are important parts of the pumping device, so that the effective upward or downward movement amount of the seat cushion is less than the manipulating amount of the user.
This prevents the manipulating force of the user that acts on the actuating lever from being efficiently transmitted to the link gear, thereby forcing the user to unnecessarily repeat the manipulation of the actuating lever and deteriorating the quality of the vehicle seats.